KR102312572B1 - The method and apparatus for performing uplink synchronization in wireless communication system - Google Patents

Abstract

The present invention relates to a method for ensuring quality of service in a wireless communication system. More specifically, the base station method according to an embodiment of the present invention includes the steps of receiving a PRACH from a terminal, and confirming a transmission pattern of the PRACH for a symbol group including a plurality of symbols, transmitted in a single tone. based on the transmission pattern of the PRACH, obtaining phase difference information between tones on which the PRACH is received according to a plurality of intervals between symbol groups, estimating a phase offset based on the phase difference information, and the estimated and generating uplink timing information for transmission to the terminal by using the timing offset converted from the phase offset.

Description

How to perform uplink synchronization in a wireless communication system

The present invention relates to a method of estimating a timing offset for acquiring uplink timing synchronization using a phase offset estimated from a PRACH signal.

Efforts are being made to develop an improved 5G communication system or pre-5G communication system in order to meet the increasing demand for wireless data traffic after the commercialization of the 4G communication system. For this reason, the 5G communication system or the pre-5G communication system is called a system after the 4G network (Beyond 4G Network) communication system or after the LTE system (Post LTE). In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as a 60 gigabyte (60 GHz) band). In order to mitigate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, in the 5G communication system, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed. In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud RAN), and an ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Technology development is underway. In addition, in the 5G system, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), and advanced access technologies such as Filter Bank Multi Carrier (FBMC), NOMA (non orthogonal multiple access), and sparse code multiple access (SCMA) are being developed.

On the other hand, the Internet is evolving from a human-centered connection network where humans create and consume information, to an IoT (Internet, of Things) network that exchanges and processes information between distributed components such as objects. Internet of Everything (IoE) technology, which combines big data processing technology through connection with cloud servers, etc. with IoT technology, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. , M2M), and MTC (Machine Type Communication) are being studied. In addition, in the IoT environment, an intelligent IT (Internet Technology) service that collects and analyzes data generated from connected objects and creates new values in human life may be provided. IoT is a field of smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart home appliance, advanced medical service, etc. can be applied to

As such, the Internet of Things (IoT), recently mentioned as one of the major services to be provided through next-generation mobile communication, is spotlighted as a driving force for continuous growth centering on related communication service providers and manufacturers, and the current related market is growing rapidly. Accordingly, 3GPP also approved the introduction of NB-IoT (Narrow Band Internet of Things) as a cellular IoT technology in response to a low-power long-distance communication standard.

The NB-IoT system may be operated in a manner of transmitting a signal using a single tone. As such, in the NB-IoT system, when a device transmits a signal for random access (eg, RACH signal) to a base station using a single tone, a method for the base station to synchronize uplink timing with the terminal is considered need to be

Accordingly, it is an object of the present invention to provide a method of estimating a timing offset from an estimated phase offset based on a transmission pattern of PRACH signals transmitted in a single tone.

A base station method according to an embodiment of the present invention for achieving the above object includes the steps of receiving a PRACH from a terminal, transmitting the PRACH in a single tone, and transmitting the PRACH for a symbol group including a plurality of symbols. Checking a transmission pattern, obtaining phase difference information between tones on which the PRACH is received according to a plurality of intervals between symbol groups based on the transmission pattern of the PRACH, estimating a phase offset based on the phase difference information and generating uplink timing information for transmission to the terminal by using the timing offset converted from the estimated phase offset.

In addition, the base station according to an embodiment of the present invention confirms the transmission pattern of the PRACH for a symbol group including a plurality of symbols, transmitted in a single tone and a communication unit receiving the PRACH from the terminal, Acquires phase difference information between tones on which the PRACH is received according to a plurality of intervals between symbol groups based on a transmission pattern of the PRACH, estimates a phase offset based on the phase difference information, and a timing offset converted from the estimated phase offset It may include a control unit that generates uplink timing information for transmission to the terminal by using .

According to an embodiment of the present invention, by estimating a phase offset based on a transmission pattern of PRACH signals transmitted in a single tone, it is possible to increase the phase offset estimation performance and obtain more accurate uplink timing synchronization. have.

1 is a conceptual diagram for explaining various operating modes in a 3GPP NB-IoT system according to an embodiment of the present invention.
2 is a diagram illustrating an example of transmitting a PRACH signal using a single tone in a wireless communication system according to an embodiment of the present invention.
3 is a diagram illustrating an example of a transmission pattern of a PRACH according to an embodiment of the present invention.
4 is a flowchart illustrating a timing offset estimation method according to an embodiment of the present invention.
5A is a flowchart illustrating a method of estimating a phase offset according to an embodiment of the present invention.
FIG. 5B is a diagram illustrating an example of a PRACH transmission pattern for explaining a method for estimating a phase offset according to FIG. 5A.
5C is a diagram schematically illustrating a method of estimating a phase offset from phase difference information for each of a plurality of symbol group intervals.
6A is a flowchart illustrating a method for estimating a phase offset.
6B is a diagram schematically illustrating a method of summing phase difference information for estimating a phase offset.
7 is a block diagram schematically illustrating a method of estimating a timing offset from an acquired phase offset according to an embodiment of the present invention.
8 is a diagram illustrating in detail a window for determining a timing offset according to an embodiment of the present invention.
9 is a block diagram illustrating a configuration of a base station according to an embodiment of the present invention.

In describing the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators. Therefore, the definition should be made based on the content throughout this specification.

In addition, in describing the embodiments of the present invention in detail, the main gist of the present invention is applicable to other communication systems having a similar technical background and channel type with slight modifications within a range not significantly departing from the scope of the present invention. And, this will be possible at the discretion of a person having technical knowledge skilled in the technical field of the present invention.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

At this time, it will be understood that each block of the flowchart diagrams and combinations of the flowchart diagrams may be performed by computer program instructions. These computer program instructions may be embodied in a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, such that the instructions performed by the processor of the computer or other programmable data processing equipment are not described in the flowchart block(s). It creates a means to perform functions. These computer program instructions may also be stored in a computer-usable or computer-readable memory that may direct a computer or other programmable data processing equipment to implement a function in a particular manner, and thus the computer-usable or computer-readable memory. It is also possible that the instructions stored in the flow chart block(s) produce an article of manufacture containing instruction means for performing the function described in the flowchart block(s). The computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operational steps are performed on the computer or other programmable data processing equipment to create a computer-executed process to create a computer or other programmable data processing equipment. It is also possible that instructions for performing the processing equipment provide steps for performing the functions described in the flowchart block(s).

Additionally, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing specified logical function(s). It should also be noted that in some alternative implementations it is also possible for the functions recited in blocks to occur out of order. For example, two blocks shown one after another may in fact be performed substantially simultaneously, or it is possible that the blocks are sometimes performed in the reverse order according to the corresponding function.

At this time, the term '~ unit' used in this embodiment means software or hardware components such as FPGA or ASIC, and '~ unit' performs certain roles. However, '-part' is not limited to software or hardware. The '~ unit' may be configured to reside on an addressable storage medium or may be configured to refresh one or more processors. Thus, as an example, '~' denotes components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, and procedures. , subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, components and '~ units' may be implemented to play one or more CPUs in a device or secure multimedia card.

Hereinafter, a method for a base station to synchronize uplink with a terminal according to an embodiment of the present invention with reference to the accompanying drawings will be described in more detail.

As in the 3GPP NB-IoT system, when the terminal transmits a signal (eg, a PRACH signal) for accessing the base station using a single tone, the terminal obtains uplink timing synchronization As an example of a method , after estimating a phase offset, a method of converting the estimated phase offset into a timing offset may be used. Here, the phase offset may be estimated using, for example, a correlation (cross correlation) between subcarriers through which signals are transmitted.

1 is a conceptual diagram for explaining various operating modes in a 3GPP NB-IoT system according to an embodiment of the present invention.

A terminal according to an embodiment of the present invention may use a single tone in transmitting and receiving a signal with a base station. In this case, the transmission of the single tone may be performed, for example, in any one of (a), (b), and (c) of FIG. 1 .

For example, as shown in Fig. 1 (a), the NB-IoT system according to an embodiment of the present invention is a GSM frequency band for the purpose of a Global System for Mobile Telecommunication (GSM) service and a potential frequency for the IoT service. It can be operated in stand-alone mode (GSM Re-farming) that exclusively provides NB-IoT service using a band. In this case, as shown in (a) of FIG. 1 , one carrier (a band of about 200 kHz) among GSM carriers may be used as a single tone.

In addition, as an example, as shown in (b) of Figure 1, the NB-IoT system according to an embodiment of the present invention, a resource block not used within the guard band (Guard-band) defined in the LTE frequency band ( resource block) to provide NB-IoT service in Guard-band mode (LTE Guard-band). In this case, the single tone shown in FIG. 1B may be used within a guard-band.

In addition, as an example, as shown in FIG. 1 ( c ), the NB-IoT system according to an embodiment of the present invention provides an NB-IoT service using a resource block within the LTE frequency band. It can be operated in -band mode (LTE In-band). In this case, as shown in (c) of FIG. 1 , one physical resource block (PRB) in the LTE frequency may be used as a single tone (180 kHz).

2 is a diagram illustrating an example of transmitting a PRACH signal using a single tone in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 2 , one block including 12 subcarriers and a time domain corresponding thereto is shown. A single tone according to an embodiment of the present invention may correspond to, for example, each of the subcarriers shown in FIG. 2 . In other words, one block shown in FIG. 2 may include 12 single tones according to an embodiment of the present invention. For example, one sub-carrier interval (fFH1) may be about 3.75 kHz.

In the system according to an embodiment of the present invention, a signal transmitted and received between the base station and the terminal may be transmitted in a single tone and a predetermined time domain corresponding to the single tone. Here, the predetermined time domain may be understood as a section corresponding to a symbol group including a plurality of symbols and a cyclic prefix (CP), as shown in FIG. 2 , for example. Hereinafter, a time domain corresponding to a single tone to which a signal is allocated according to an embodiment of the present invention will be described using the term symbol group.

For example, the PRACH signal according to an embodiment of the present invention may be transmitted based on a plurality of repetition intervals during a transmission time during which the PRACH signal is transmitted. For example, one PRACH signal transmission period may include a maximum of 128 repetition periods. In addition, one repetition period may consist of 4 symbol groups and 12 tones. For example, as shown in FIG. 2 , one symbol group may have a time domain corresponding to about 0.4 ms, and one repetition period may have a time domain corresponding to four symbol groups (1.6 ms). have.

In addition, each of the plurality of repetition periods for transmitting the PRACH signal may be preset as a PRACH transmission pattern corresponding to a specific terminal. That is, when the PRACH signal according to an embodiment of the present invention is transmitted to a specific terminal, it may be transmitted according to a preset repetition interval corresponding to the specific terminal. In other words, the PRACH transmission pattern may refer to a pattern for a position of a tone to which a PRACH signal is allocated corresponding to each of a plurality of symbol groups included in each of a plurality of repetition periods.

For example, the PRACH transmission pattern of the first repetition period (repetition 0) shown in FIG. 2 is allocated such that the PRACH signal 20a is transmitted in the first symbol group and tone 0, and the second symbol group is the first The PRACH signal 20b is allocated to be transmitted on a tone (tone 2) having a tone interval of one tone from the second symbol group, and the third symbol group is a tone having a tone interval of 6 tones with the second symbol group (tone 7). ), the PRACH signal 20c is allocated to be transmitted, and the fourth symbol group may be a pattern allocated so that the PRACH signal 20d is transmitted in one tone interval (tone 6) with the third symbol group.

When the PRACH signal is transmitted in this way, the base station may estimate a phase offset by performing cross-correlation between adjacent symbol groups. Also, the base station according to an embodiment of the present invention may obtain uplink synchronization by converting the estimated phase offset into a timing offset. In this case, when the PRACH signal is received through each of the plurality of antennas, the base station may perform phase offset estimation after combining signals received from each of the antennas.

More specifically, the base station can obtain a cross-correlation value between adjacent symbol groups using the following [Equation 1], and the phase offset estimated therefrom can be converted into a timing offset through the following [Equation 2]. have.

[Equation 1]

Here, a denotes an index of an antenna, and Ra(k) denotes a cross-correlation value between signals having k tone intervals in the antenna a. For example, as shown in FIG. 2 , when PRACH is transmitted, Ra(k) is a cross-correlation value between PRACH signals corresponding to tones 1 and 2, respectively, and tones 7 and 6 respectively. It may include a cross-correlation value between PRACH signals, and the like.

[Equation 2]

Here, angle(R(k)) may mean a value in radians for a phase angle of the cross-correlation value obtained in [Equation 1]. That is, the base station according to an embodiment of the present invention may derive a timing offset for obtaining uplink synchronization from the phase offset using [Equation 2].

3 is a diagram illustrating an example of a transmission pattern of a PRACH according to an embodiment of the present invention.

As described above in FIG. 2 , the PRACH signal may be transmitted based on a transmission pattern of a PRACH preset corresponding to one UE, and the transmission pattern of the PRACH may include a plurality of repetition periods. 3 illustrates a first repetition interval (repetiton 0) to a fourth repetition interval (repetiton 3) included in a transmission pattern of a PRACH.

As described above with reference to FIG. 2 , in the PRACH transmission pattern, the pattern for the position of the tone through which the PRACH signal is transmitted in each of the symbol groups included in one repetition period may be preset. However, a pattern regarding the position of a tone through which a PRACH signal is transmitted between one repetition interval and an adjacent symbol group between one repetition interval may be randomly determined.

For example, as shown in FIG. 3 , a PRACH signal allocated to be transmitted in the fourth symbol group of the first repetition period (repetiton 0) and a PRACH signal allocated to be transmitted in the first symbol group of the second repetition period (repetiton 1) The tone interval between the two may be randomly determined.

Meanwhile, cross-correlation for estimating a phase offset according to an embodiment of the present invention may be performed based on an interval between symbol groups. In other words, cross-correlation according to an embodiment of the present invention may be performed between PRACH signals corresponding to each of two symbol groups selected based on an interval of a predetermined symbol group. Here, the interval between symbol groups for cross-correlation may be determined based on, for example, one repetition period.

For example, within one repetition period, PRACH signals having one symbol group interval may be selected. Referring to the first repetition period (repetition 0) of FIG. 3 , the base station according to an embodiment of the present invention includes a first symbol group 31 , a second symbol group 32 , and a second symbol group 32 . ), the third symbol group 33 , and the third symbol group 33 and the fourth symbol group 34 can be selected.

In addition, the base station according to an embodiment of the present invention has a first symbol group 31, a third symbol group 33, and a second symbol group having an interval of two symbols within a first repetition period (repetition 0). A symbol group 32 and a fourth symbol group 34 can be selected.

In addition, the base station according to an embodiment of the present invention can select the first symbol group 31 and the fourth symbol group 34 having three symbol group intervals within the first repetition period (repetition 0). have.

Meanwhile, in the NB-IoT system according to an embodiment of the present invention, in the case of estimating the timing offset, according to the conventional method described above with reference to FIG. 2 , a cross-correlation value between PRACH signals having one symbol group interval. can be used to estimate the phase offset. That is, there is a problem that a cross-correlation value between RPACH signals having two or three symbol group intervals cannot be used for estimating a phase offset, so that a more appropriate timing offset value cannot be obtained. Hereinafter, a method for utilizing cross-correlation values of PRACH signals based on a plurality of symbol group intervals will be described.

4 is a flowchart illustrating a timing offset estimation method according to an embodiment of the present invention.

Referring to FIG. 4 , the base station according to an embodiment of the present invention may receive a PRACH from the terminal (S410).

As described above with reference to FIG. 3 , the terminal according to an embodiment of the present invention may transmit the PRACH according to a transmission pattern preset in response to the terminal. That is, the PRACH according to an embodiment of the present invention may be transmitted according to a transmission pattern including a plurality of repetition intervals, and one repetition interval may include a plurality of symbol groups. In addition, in one repetition period, the PRACH may be transmitted at one symbol group and a position of a preset tone corresponding thereto.

In this way, when the PRACH signal is received, the base station according to an embodiment of the present invention may check a PRACH transmission pattern for a symbol group including a plurality of symbols, which is transmitted on a single tone (S420).

For example, the base station according to an embodiment of the present invention provides a PRACH such as the number of repetition intervals in which the PRACH is transmitted, the number of symbol groups included in each repetition interval, and the position of a tone to which the PRACH is allocated corresponding to the symbol group. You can check the transmission pattern of And, the base station according to an embodiment of the present invention may check whether the PRACH transmitted from the terminal is transmitted according to a preset repetition pattern corresponding to the terminal.

In addition, the base station according to an embodiment of the present invention may acquire phase difference information between tones on which PRACH is received according to a plurality of intervals between symbol groups based on the transmission pattern of the PRACH ( S430 ).

Here, the phase difference information may include information on a cross-correlation value obtained from tones through which any two PRACHs selected based on a transmission pattern of the PRACH are transmitted. More specifically, the phase difference information determines the symbol group interval based on the transmission pattern of the PRACH, and cross-correlation is performed using the tone (frequency) information of each of the two PRACH signals having the determined symbol group interval. Correlation results may be included. A method of obtaining the phase difference information will be described later in more detail with reference to FIGS. 5A, 5B, and 5C.

The base station according to an embodiment of the present invention may determine a plurality of different symbol group intervals based on a PRACH transmission pattern, and obtain phase difference information based on each of the plurality of symbol group intervals.

As such, when the phase difference information is obtained, the base station according to an embodiment of the present invention may estimate a phase offset based on the obtained phase difference information (S440). Then, the base station according to an embodiment of the present invention may generate uplink timing information for transmission to the terminal by using the timing offset converted from the estimated phase offset (S450).

As described above, the base station according to an embodiment of the present invention obtains phase difference information based on each of a plurality of symbol group intervals, and converts the phase offset estimated therefrom to obtain a timing offset for generating uplink timing information. can be obtained Therefore, according to the method according to an embodiment of the present invention, since all cross-correlation values between PRACH signals having various symbol group intervals can be used, the estimation performance of the phase offset can be increased, and thus more accurate up There is an effect that the link timing information can be transmitted to the terminal.

5A is a flowchart illustrating a method for estimating a phase offset according to an embodiment of the present invention, and FIG. 5B is a diagram illustrating an example of a PRACH transmission pattern for explaining a method for estimating a phase offset according to FIG. 5A. . 5C is a diagram schematically illustrating a method of estimating a phase offset from phase difference information for each of a plurality of symbol group intervals.

First, referring to FIG. 5A , the base station according to an embodiment of the present invention may select one of a plurality of symbol group intervals in order to obtain phase difference information for each of the plurality of symbol group intervals. That is, the base station according to an embodiment of the present invention determines a predetermined symbol group interval among a plurality of symbol group intervals, and selects an arbitrary first symbol group and a second symbol group having the determined predetermined symbol group interval. can be (S510).

More specifically, it will be described with reference to FIG. 5B. For example, the base station according to an embodiment of the present invention may select two symbol groups based on one symbol group interval (the interval of A).

For example, the base station includes a first symbol group 50 and a second symbol group 51, a second symbol group 51 and a third symbol group 52, and three The fourth symbol group 52 and the fourth symbol group 53 may be selected. Also, the base station may select the fourth symbol group 53 of the first repetition period (repetition 0) and the first symbol group 54 of the second repetition period (repetition 1). As such, in the base station according to an embodiment of the present invention, in the entire transmission period of the PRACH (in the case of FIG. 5B as an example, the period from the first repetition period (repetition 0) to the fourth repetition period (repetiton 3)) A plurality of symbol group pairs for one symbol group interval can be selected.

Also, for example, the base station according to an embodiment of the present invention may select two symbol groups based on the two symbol group intervals (interval B).

For example, the base station selects the first symbol group 50 and the third symbol group 52, the second symbol group 51 and the fourth symbol group 53 included in the first repetition period (repetiton 0). can Also, the base station may select the third symbol group 52 of the first repetition period (repetition 0) and the first symbol group 54 of the second repetition period (repetition 1). As such, in the base station according to an embodiment of the present invention, in the entire transmission period of the PRACH (in the case of FIG. 5B as an example, the period from the first repetition period (repetition 0) to the fourth repetition period (repetiton 3)) A plurality of symbol group pairs for two symbol group intervals can be selected.

Also, as an example, the base station according to an embodiment of the present invention may select two symbol groups based on a three symbol group interval (interval C).

For example, the base station may select the first symbol group 50 and the fourth symbol group 53 included in the first repetition period (repetiton 0). Also, the base station may select the second symbol group 51 of the first repetition period (repetition 0) and the first symbol group 54 of the second repetition period (repetition 1). As such, in the base station according to an embodiment of the present invention, in the entire transmission period of the PRACH (in the case of FIG. 5B as an example, the period from the first repetition period (repetition 0) to the fourth repetition period (repetiton 3)) A plurality of symbol group pairs for three symbol group intervals can be selected.

Referring back to FIG. 5A , the base station according to an embodiment of the present invention selects a first symbol group and a second symbol group based on a predetermined symbol group interval, and the PRACH and the second symbol corresponding to the first symbol group Cross-correlation may be performed using the PRACH corresponding to the group (S520).

More specifically, the base station according to an embodiment of the present invention may derive a cross-correlation value using tone information of the PRACH corresponding to each of the first symbol group and the second symbol group selected based on one symbol group interval. have. In this case, since a plurality of pairs of the first symbol group and the second symbol group may be selected based on one symbol group interval, a plurality of cross-correlation values for one symbol group interval may be derived.

The base station according to an embodiment of the present invention obtains a plurality of cross-correlation values obtained for one symbol group interval as phase difference information for the predetermined symbol group interval, and phase difference information for each of a plurality of symbol group intervals can be obtained.

Also, the base station according to an embodiment of the present invention may sum the phase difference information on which cross-correlation is performed for a predetermined symbol group interval in a preset manner ( S530 ).

That is, the base station according to an embodiment of the present invention may sum a plurality of cross-correlation values derived for a predetermined symbol group interval in a preset manner. Here, a method of summing a plurality of cross-correlation values will be described later with reference to FIGS. 6A and 6B .

In addition, the base station according to an embodiment of the present invention may estimate the result values summed in a preset manner for a plurality of symbol group intervals as a phase offset ( S540 ).

As described above, the base station according to an embodiment of the present invention has the effect of increasing estimation performance by estimating the phase offset from cross-correlation values obtained based on a plurality of intervals between symbol groups in which the PRACH is received. .

The above-described phase offset estimation method will be described with reference to FIG. 5C, which is more schematic.

The base station according to an embodiment of the present invention may receive signals through a plurality of antennas. In this case, the base station according to an embodiment of the present invention may add (hereinafter, referred to as coherent combining) signals received on the same tone among signals received from each antenna before acquiring the phase difference information. Hereinafter, y _a [i] may mean a signal on which coherent combining is performed on signals received from antenna a.

In the above formula, i may be an index of a symbol group, and t may mean an index of symbols included in the symbol group of i. In one embodiment of the present invention, a case in which five symbols are included in one symbol group will be described.

As shown in FIG. 5C , the base station according to an embodiment of the present invention may use a signal y _a [i] on which coherent combining is performed as an input signal. The base station according to an embodiment of the present invention may determine a predetermined symbol group interval d, select symbol groups having a symbol group interval d, and perform cross-correlation. For example, in FIG. 5C , the input signal y _a [i] is input to the block 5a of delay 1 when the symbol group interval d is determined to be 1, and is input to the block 5a of delay 2 when the symbol group interval d is determined to be 2 ( 5b) can be entered.

And, the base station according to an embodiment of the present invention may derive the cross-correlation value of the signals input to each delay block by using the following equation.

Here, y _a [i] and y _a [id] may mean symbol groups having a symbol group interval of d. For example, y _a [i] may mean a first symbol group received from antenna a, and y _a [id] may mean a second symbol group received from antenna a. The base station according to an embodiment of the present invention may input cross-correlation values derived for each antenna to the summing block 15a using PRACHs having a symbol group interval of d. In addition, the base station according to an embodiment of the present invention may obtain phase difference information R _d [i] obtained by summing cross-correlation values derived for each antenna for a plurality of antennas using the summing block 15a.

Here, R _d [i] may mean phase difference information for a symbol group interval of d. For example, referring to FIG. 5B , as an example, in the first repetition period (repetiton 0), R ₁ [1] is the signal y _a [1] for the first symbol group 50 and the second symbol group (51) _{the cross-correlation value between the signals for y a} [2], the cross-correlation between the signal y _a [2] for the second symbol group 51 and the signal y _a [3] for the third symbol group 52 It may mean the sum of values and cross-correlation values of the signal y _a [3] for the third symbol group 52 and the signal y _{a [4] for the fourth symbol group 53 .}

As described above, the base station according to an embodiment of the present invention uses signals received from a plurality of antennas to obtain a plurality of phase difference information (R ₁ [i], R ₂ [i], R ₃ [i] for each symbol group interval) ], R ₄ [i]), summing for summing a plurality of phase difference information (R ₁ [i], R ₂ [i], R ₃ [i], R ₄ [i]) in a preset manner It can be input with a group 25 (correlation value combiner). The values output from the summer 25 may be estimated as a phase offset value according to an embodiment of the present invention.

Hereinafter, a method of estimating the phase offset will be described in more detail with reference to FIGS. 6A and 6B .

6A is a flowchart illustrating a method for estimating a phase offset, and FIG. 6B is a diagram schematically illustrating a method of summing phase difference information for estimating a phase offset.

First, referring to FIG. 6A , the base station according to an embodiment of the present invention may classify a plurality of phase difference information obtained with respect to a predetermined symbol group interval by tone intervals corresponding to each of the plurality of phase difference information ( S610).

More specifically, as described above, a plurality of symbol group pairs selected based on one symbol group interval are in the transmission period of the PRACH, and cross-correlation values for each of the plurality of symbol group pairs are in the one symbol group interval. may be obtained as a plurality of phase difference information. The base station according to an embodiment of the present invention may classify a plurality of phase difference information based on tone interval information of each symbol group of a symbol group pair used to generate the plurality of phase difference information.

For example, the base station according to an embodiment of the present invention selects a first symbol group and a second symbol group in order to generate phase difference information for one symbol group interval, and selects a PRACH corresponding to the first symbol group and First phase difference information obtained by performing cross-correlation between PRACHs corresponding to the second symbol group may be obtained. Similarly, the base station according to an embodiment of the present invention selects a third symbol group and a fourth symbol group having one symbol group interval, and a PRACH corresponding to the third symbol group and a PRACH corresponding to the fourth symbol group. Second phase difference information on which cross-correlation is performed may be obtained.

In addition, the base station according to an embodiment of the present invention may classify the first phase difference information and the second phase difference information according to the tone interval information. For example, the base station according to an embodiment of the present invention may map the tone interval information between the tone corresponding to the first symbol group and the tone corresponding to the second symbol group and the first phase difference information. In addition, the base station according to an embodiment of the present invention may map the tone interval information between the tone corresponding to the third symbol group and the tone corresponding to the fourth symbol group and the second phase difference information.

Here, the tone interval information may include information on the size of the tone interval and the phase sign information of the tone interval. For example, when the tone corresponding to the first symbol group is tone 0 and the tone corresponding to the second symbol group is tone 7, the tone interval information is the reference phase code (eg, positive phase code) of It may have a tone interval size of 7. As another example, when the tone corresponding to the third symbol group is tone 5 and the tone corresponding to the fourth symbol group is tone 2, the tone interval information is an opposite phase sign (eg, negative It may have a tone interval size of 3 of the phase sign).

In this way, the base station according to an embodiment of the present invention, as shown in FIG. 6B, transmits a plurality of phase difference information (eg, R1[i]) acquired for one symbol group interval to the serial block 60 ) can be entered. In addition, the base station according to an embodiment of the present invention inputs each of a plurality of phase difference information arranged in a row by the serial block 60 to the classification block 61, and a tone interval between symbol groups related to each of the plurality of phase difference information. Based on the information, each of the plurality of phase difference information may be classified by mapping the corresponding tone interval information.

In this case, the base station according to an embodiment of the present invention may check the sign of the phase corresponding to each of the classified phase difference information based on the tone interval information ( S620 ).

Here, as described above, the phase code may be determined according to whether the direction of the tone interval is positive or negative with respect to the delay direction of the symbol group in which the PRACH is transmitted.

The base station according to an embodiment of the present invention adds up the phase difference information in which the sign of the phase is confirmed as the reference code as it is, and performs a separate operation on the phase difference information in which the sign of the phase is confirmed as the opposite sign of the reference code. That is, the base station according to an embodiment of the present invention may perform a conjugate operation on phase difference information corresponding to opposite phase codes (S630).

As shown in FIG. 6B , the phase difference information corresponding to the opposite phase sign is input to the complex operation block 62 and may be summed while the conjugate operation is performed.

In addition, the base station according to an embodiment of the present invention may add the phase difference information corresponding to the reference code and the phase difference information on which the conjugate operation is performed (S640).

In other words, the base station according to an embodiment of the present invention may classify phase difference information for one symbol group interval, and add the classified phase difference information based on the sign of the corresponding phase. When phase difference information is summed for each of the plurality of symbol group intervals in this way, the base station according to an embodiment of the present invention may estimate the summed result values as a phase offset.

Hereinafter, a method of generating a timing offset and uplink timing information from a phase offset according to an embodiment of the present invention will be described with reference to FIGS. 7 and 8 .

7 is a block diagram schematically illustrating a method of estimating a timing offset from a phase offset obtained according to an embodiment of the present invention, and FIG. 8 is a detailed view of a window for determining a timing offset according to an embodiment of the present invention. It is a drawing.

First, referring to FIG. 7 , a plurality of phase offsets estimated according to the above-described method may be transmitted and input to a timing offset conversion block. For example, when a Fast Fourier Transform (FFT) having a size of 512 is used for the timing offset transform block, 11 phase offset values may be input to the zero bit inserter 710 as shown in FIG. 7 . have. The zero bit inserter 710 may output a plurality of phase offset values to output terminals 1 to 11, and apply 0 to output terminals 12 to 512 to output them.

The values output from the zero bit inserter 710 may be input to the FFT 720 . The FFT 720 may perform Fourier transform using the input phase offset values and 0, and may output a result value through 512 output terminals. In addition, the values output from the FFT 720 may be output only values corresponding to real numbers through the real number obtaining unit 730 .

Thereafter, the real values output from the real number acquisition unit 730 may be input to the window unit 740 . The window unit 740 acquires only values within a predetermined window range among the values output from the real number obtainer 730, and overwrites values not included within the predetermined window range with 0. can

More specifically, referring to FIG. 8 , the window unit 840 includes a pre-window (pre-window, 840a) range, a post-window (840b) range, and a window (post + pre window) in which the post and pre-window are combined. , 840c) range may be set. The window unit 840 may overwrite values not included in the window ranges by applying the window ranges to the values input from the real number obtaining unit 730 according to a preset condition.

Thereafter, values obtained based on the window ranges may be input to the timing offset determiner 750 . The timing offset determiner 750 may determine a timing offset value by selecting a maximum value from among the values input from the window unit 840 .

The base station according to an embodiment of the present invention may generate uplink timing information for uplink timing synchronization with the terminal based on the determined timing offset value. And, the base station according to an embodiment of the present invention may transmit the generated uplink timing information to the terminal that has transmitted the PRACH.

9 is a block diagram illustrating a configuration of a base station according to an embodiment of the present invention. With reference to FIG. 9, the operation of the above-described base station will be described.

As shown in FIG. 9 , the base station according to an embodiment of the present invention may include a communication unit 910 and a control unit 920 .

The communication unit 910 according to an embodiment of the present invention may include an antenna, a GAP&CP remover 911 , a frequency shifter 912 , and an adaptive gain controller (AGC) 913 .

More specifically, when a signal is received through the antenna of the base station according to an embodiment of the present invention, the GAP&CP removing unit 911 may remove GAP and CP (Cyclic Prefix) included in the PRACH signal. As described above, the signal from which the GAP and CP are removed may be input to the frequency shifter 912 , frequency shifting may be performed, and may be input to the AGC 913 and adjusted to a signal included in a preset bit region.

As such, the signal preprocessed by the communication unit 910 may be input to the control unit 920 for timing offset estimation according to an embodiment of the present invention. The controller 920 according to an embodiment of the present invention includes a PRACH transmission pattern checker 921 , a phase difference information obtainer 922 , a phase offset estimator 923 , a timing offset estimator 924 , and a timing information generation portion 925 .

More specifically, the PRACH transmission pattern check unit 921 may check the transmission pattern of the PRACH received from the terminal. That is, the PRACH transmission pattern checker 921 may check a plurality of repetition intervals of the PRACH, and check the transmission pattern of the PRACH from symbol groups included in each repetition interval and tone information corresponding to each of the symbol groups.

In addition, the phase difference information obtaining unit 922 may perform an operation for obtaining the phase difference information by using the PRACH transmission pattern information confirmed by the PRACH transmission pattern checking unit 921 . More specifically, the phase difference information obtaining unit 922 may determine a symbol group interval for obtaining the phase difference information based on the confirmed PRACH transmission pattern. That is, the delay blocks 5a and 5b described above in FIG. 5C may be included in the phase difference information obtaining unit 922 . In addition, a pair of symbol groups having a determined symbol group interval may be selected, and cross-correlation may be performed using PRACH signals corresponding to the selected symbol group pair. The phase difference information obtaining unit 922 may sum a plurality of cross-correlation values obtained in one symbol group interval for each antenna. That is, the summing block 15 described above in FIG. 5C may be included in the phase difference information obtaining unit 922 .

As such, when phase difference information for each of the plurality of symbol group intervals is obtained by the phase difference information obtaining unit 922 , the phase offset estimating unit 923 may estimate the phase offset. More specifically, the phase offset estimator 923 lists the phase difference information for each of the plurality of intervals through a serial block (see 60 of FIG. 6B ), and then adds the phase difference information to the tone interval information between symbol groups corresponding to each of the phase difference information. Based on the classification block (refer to 61 of FIG. 6B ), each of the phase difference information may be classified.

Also, the phase offset estimator 923 may determine the information to be conjugated from among the phase difference information by checking the sign of the phase corresponding to the phase difference information classified as described above. That is, the phase offset estimator 923 may perform a conjugate operation on phase difference codes having opposite phase codes using a complex operation block (see 62 of FIG. 6B ). Thereafter, the phase offset may be estimated by summing the phase difference information having the reference phase code and the phase difference information on which the conjugate operation is performed.

The timing offset estimator 924 according to an embodiment of the present invention may estimate the estimated phase offset using the blocks described above with reference to FIG. 7 . That is, the timing offset estimator 924 inserts a zero bit into a plurality of phase offset values, performs a Fourier transform, and then uses a preset window among values to which the Fourier transform is performed to a value included within a specific window range. can choose In addition, the timing offset estimator 924 may estimate a maximum value among values included within a specific window range as the timing offset.

The estimated timing offset value may be generated as uplink timing information by the timing information generating unit 925 according to an embodiment of the present invention, and then transmitted to the terminal through the communication unit 910 .

Those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims described below rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. should be interpreted

On the other hand, in the present specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms are used, these are only used in a general sense to easily explain the technical content of the present invention and help the understanding of the present invention, It is not intended to limit the scope of the invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (16)

A method for performing uplink synchronization of a base station in a wireless communication system, the method comprising:
Receiving a PRACH from the terminal;
checking a transmission pattern of the PRACH for a symbol group including a plurality of symbols, which is transmitted in a single tone;
obtaining phase difference information between tones on which the PRACH is received according to a plurality of intervals between symbol groups based on the transmission pattern of the PRACH;
estimating a phase offset based on the phase difference information; and
and generating uplink timing information for transmission to the terminal by using the timing offset converted from the estimated phase offset. According to claim 1,
The step of obtaining the phase difference information includes:
selecting a first symbol group and a second symbol group having a predetermined interval from among the plurality of intervals;
obtaining phase difference information for the predetermined interval from a cross-correlation value between a PRACH corresponding to the first symbol group and a PRACH corresponding to the second symbol group; and
and acquiring the phase difference information for each of the plurality of intervals. 3. The method of claim 2,
The step of estimating the phase offset comprises:
accumulating phase difference information for the predetermined interval in a preset manner; and
and estimating, as the phase offset, result values of the summing for each of the plurality of intervals. 4. The method of claim 3,
The step of summing in the preset method comprises:
classifying the phase difference information for the predetermined interval for each tone interval; and
and a summing step of summing the phase difference information corresponding to each tone interval. 5. The method of claim 4,
The summing step is
checking a sign of a phase corresponding to each of the classified phase difference information;
performing a complex operation on the phase difference information when the sign of the phase is opposite to the reference sign; and
and summing the phase difference information corresponding to the reference code and the phase difference information on which the complex operation is performed. According to claim 1,
The transmission pattern of the PRACH is confirmed based on a plurality of repetition intervals in which the PRACH is transmitted,
Each of the repetition intervals, the base station method, characterized in that it includes a preset number of symbol groups. 4. The method of claim 3,
wherein the timing offset is derived by converting a phase offset for each of the plurality of intervals into a time domain. 8. The method of claim 7,
generating as the uplink timing information a value selected based on a preset window among the values converted into the time domain; and
The method further comprising transmitting the generated uplink timing information to the terminal. In a base station of a wireless communication system,
a communication unit for receiving the PRACH from the terminal; and
Check the transmission pattern of the PRACH for a symbol group including a plurality of symbols, transmitted in a single tone, and the PRACH received tone according to a plurality of intervals between symbol groups based on the transmission pattern of the PRACH Obtaining phase difference information between the two, estimating a phase offset based on the phase difference information, and using a timing offset converted from the estimated phase offset, comprising a control unit for generating uplink timing information for transmission to the terminal Base station, characterized in that. 10. The method of claim 9,
The control unit is
A first symbol group and a second symbol group having a predetermined interval are selected from among the plurality of intervals, and the predetermined symbol group is selected from the cross-correlation value between the PRACH corresponding to the first symbol group and the PRACH corresponding to the second symbol group. The base station, characterized in that after obtaining the phase difference information for the interval, the phase difference information is obtained by obtaining the phase difference information for each of the plurality of intervals. 11. The method of claim 10,
The control unit is
The base station according to claim 1, wherein the phase difference information for the predetermined interval is accumulated in a preset manner, and result values obtained by performing the summation for each of the plurality of intervals are estimated as the phase offset. 12. The method of claim 11,
The control unit is
and classifying the phase difference information for the predetermined interval for each tone interval, and summing the phase difference information corresponding to each tone interval. 13. The method of claim 12,
The control unit is
A sign of a phase corresponding to each of the classified phase difference information is checked, and when the sign of the phase is opposite to a reference sign, a complex operation is performed on the phase difference information, and the phase difference corresponding to the reference sign A base station, characterized in that the information and the phase difference information on which the complex operation is performed is summed. 10. The method of claim 9,
The control unit checks a transmission pattern of the PRACH based on a plurality of repetition intervals in which the PRACH is transmitted,
Each of the repetition intervals is a base station, characterized in that it includes a preset number of symbol groups. 12. The method of claim 11,
The control unit, the base station, characterized in that for deriving the timing offset by converting the phase offset for each of the plurality of intervals into a time domain. 16. The method of claim 15,
The control unit is
The base station, characterized in that for controlling the communication unit to generate a value selected based on a preset window among the time-domain converted values as the uplink timing information, and to transmit the generated uplink timing information to the terminal.

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